This invention relates to a flexible composite material component, for example to a component comprising a fibre material impregnated with a resin material. The invention relates in particular to a flexible component suitable for use in the transmission of rotary drive. However, it will be appreciated that the invention may be employed in other applications, for example in fuel pipes and pipes or hoses for conveying other fluids.

Composite materials such as carbon or glass fibres or the like impregnated with suitable resins are in increasingly widespread use in a wide range of applications. The materials are of relatively low weight and good strength, and so are advantageous in a number of applications in which it is desirable to make weight savings. By way of example, the materials are employed in a number of aerospace and automotive applications in which making weight savings can lead to improvements in fuel efficiency.

In some applications, there is a need for certain components to be capable of undergoing limited flexing, for example to accommodate slight misalignments between other components or to accommodate movement between other components as may occur due to differential thermal expansion and other effects. By way of example, this may be required in certain torque transmission applications or where used in conveying fluids.

The designs of components manufactured from composite materials may result in the components being of limited inherent flexibility. By way of example, in manufacturing a component in such a manner as to have predetermined strength characteristics resisting twisting thereof, the component may be so stiff that it has only a very restricted level of axial flexibility. The restricted level of flexibility may restrict or prevent the use of composite materials in some applications, for example where a degree of axial misalignment must be accommodated. It is an object of the invention to provide a composite material component in which the flexibility thereof may be enhanced.

According to the present invention there is provided a composite material component comprising a first composite material layer, a second composite material layer, and an interlayer located between the first and second composite material layers in at least a region of the component, the interlayer preventing direct bonding between the first and second composite material layers at the said region.

By preventing direct bonding between the first and second layers at the said region, relative movement between the layers is accommodated, in use, resulting in the said region of the component being of relatively good flexibility.

The interlayer may take the form of a flexible component. By way of example, it may be of a rubber or rubber-like material. The interlayer may be bonded to the first and second layers. In such an arrangement, in order for relative movement to occur between the first and second layers at the said region, shearing movement of the interlayer will occur. By appropriate selection of the material of the interlayer, control over the level of flexibility present in the component may be achieved.

Alternatively, the interlayer may be bonded to only one, or neither, of the first and second layers. In such an arrangement, the interlayer may not need to undergo shearing movement, in use. Instead, a degree of sliding movement may occur between the interlayer and one or other, or both, of the layers.

The component may be formed in such a manner as to include hoop windings adjacent end parts of the interlayer. Such hoop windings may be arranged to resist delamination of the first and second layers close to the end parts of the interlayer. As a result, the component may be of enhanced durability. However, it is envisaged that such hoop windings will not always be required.

The component may take the form of a drive shaft. By way of example, it may be of hollow tubular form. The component may include one or more parts of generally S- or U-shaped cross- sectional shape to aid flexing thereof. The said region is preferably located within a curved part of the or at least one of the S- or U-shaped parts.

Alternatively, the component may take the form of a drive disc including one or more flexible regions.

The component is preferably of a fibre reinforced resin material. By way of example, it may comprise a resin impregnated wound fibre component, for example of carbon or glass fibre form. However, other materials are possible. By way of example, it may comprise woven fibre material layers, or the like, laid upon one another.

The invention also relates to a method of manufacture of a flexible composite material component comprising the steps of forming an assembly comprising a first composite material layer, a second composite material layer, and an interlayer located between the first and second composite material layers in at least a region of the component, the interlayer preventing direct bonding between the first and second composite material layers at the said region, an curing the composite material(s) of the first and second layers.

The invention will further be described, by way of example, with reference to the accompanying drawings, in which:

Figure 1 is a diagrammatic cross-sectional view of part of a component in accordance with an embodiment of the invention; and Figures 2 and 3 are diagrammatic views illustrating components in accordance with embodiments of the invention.

Referring firstly to Figures 1 and 2, a drive shaft 10 is illustrated. The drive shaft 10 is of hollow tubular form and includes, at its ends, fittings 12 arranged to allow the drive shaft 10 to be secured to other components (not shown) which are substantially axially aligned with one another. The drive shaft 10 is of wound fibre composite material form, manufactured by winding a fibre material onto a mandrel of a suitable shape, impregnating the fibre with a suitable resin material, and curing the resin material or allowing the resin material to cure. The fibre material is wound in such a manner as to form a number of composite material layers wound one upon another.

The precise shape of the drive shaft 10, and dimensions thereof, will depend upon the application in which the drive shaft 10 is to be employed. In some applications it will be of relatively great length. In other applications, it may be required to be of shorter length. Similarly, in some applications it will be of relatively small diameter, and in other applications it may be of larger diameter, for example accommodating other parts of the device or apparatus with which it is used within the interior thereof. Where the components to which the drive shaft 10 is connected are not exactly, accurately aligned with one another, then flexing of the drive shaft 10 is required to take place, in use.

In order to promote flexing of the drive shaft 10, the drive shaft 10 is shaped to define an enlarged diameter region 14 of smoothly curved, generally U-shaped form. Flexing of the base 16 of the region 14 allows the limbs 18 thereof to flex towards or away from one another, allowing the drive shaft 10 to take on a slightly bent form. As the drive shaft 10 rotates, in use, the direction in which it is bent will change, the drive shaft 10 flexing to accommodate the aforementioned slight misalignment. Whilst a smoothly curved generally U-shaped region 14 is illustrated, other forms are possible. For example, the region 14 may be of generally S-shaped or C-shaped form. As best shown in Figure 1, the drive shaft 10 includes a first component material layer 20 and a second composite material layer 22. A number of other composite material layers may also be present wound upon or beneath the layers 20, 22. At the base 16 of the region 14, an interlayer 24 is located between the first and second layers 20, 22. The interlayer 24, in this embodiment, takes the form of a component of a rubber or rubber-like material that is fitted onto the fibres forming the first layer before subsequently winding the fibres forming the second layer, the windings forming the second layer being wound, at least in part, over the component of rubber or rubber-like material.

After curing of the resin material impregnated into the fibres of the drive shaft 10, the interlayer 24 will be bonded to both the first and second layers 20, 22.

If desired, prior to curing of the resin, one or more hoop windings 26 may be wound adjacent the ends of the interlayer 24, the purpose of which is to resist delamination of the first and second layers 20, 22 in this region.

It will be appreciated that, in use, the presence of the interlayer 24 prevents direct bonding between the first and second layers 20, 22 at the location of the interlayer 24. Consequently, limited shearing movement of the first layer 20 relative to the second layer 22 may occur, the interlayer 24 flexing or shearing to accommodate such shearing movement. The limited relative shearing movement between the first and second layers 20, 22 promotes flexing of the region at which the interlayer 24 is located, and hence flexing of the drive shaft 10 as a whole. Elsewhere, where the first and second layers 20, 22 are directly bonded to one another, a higher resistance to shearing movement between the layers 20, 22 will be experienced, and so the shaft 10 will be of higher stiffness and less flexible form.

By designing the first and second (and other) layers 20, 22 of the drive shaft 10 in such a manner as to achieve the desired strength and torque transmitting properties, it will be appreciated that the enhanced flexibility may be achieved in a drive shaft 10 satisfying other strength characteristics.

Whilst in the arrangement described hereinbefore the interlayer 24 takes the form of a component of a rubber or rubber-like material that, in use, is bonded to the first and second layers 20, 22, it will be appreciated that this need not always be the case. By way of example, the interlayer may be bonded to just one of the layers 20, 22, relative movement being permitted between the interlayer 24 and the other of the layers 20, 22 without requiring shearing or other deformation of the interlayer 24 to occur. Again, it will be appreciated that the presence of the interlayer 24 promotes flexibility of at least part of the drive shaft 10.

Furthermore, the interlayer 24 may not be bonded to either the first layer 20 or the second layer 22, if desired.

Although reference is made to the use of rubber or rubber-like materials for the interlayer 24, other materials that may be used include, for example, PTFE material elements. Where the material of the interlayer 24 would not normally bond to the layers 20, 22, and such bonding is desired, then a suitable coating may be applied to the interlayer 24 to promote such bonding.

Figure 3 illustrates the application of the invention to a component in the form of a torque transmitting drive disc 30. The disc 30 includes a plurality of lobes 28a to be secured, for example using bolts or the like, to one drive component, and a second plurality of lobes 28b to be secured, in use, to another drive component. In use, flexing of the disc 30 accommodates misalignment between the drive components whilst allowing the transmission of torque therebetween via the disc 30.

The disc 30 is manufactured by forming an assembly comprising a series of layers of woven fabrics or the like, for example woven from glass or carbon fibres, the assembly being impregnated with a suitable resin material. As with the arrangement of Figures 1 and 2, an interlayer is located between a first one of the layers and a second one of the layers in a region of the disc 30 to prevent direct bonding therebetween at the region, and thereby promote flexing of that region of the disc 30. The flexible regions may be located, for example, at the points 32 where the lobes 28a, 28b merge into a central part 34 of the disc 30.

Whilst the description hereinbefore is of torque transmitting components, it will be appreciated that the invention may be used in other applications, for example in pipes, hoses or the like intended to be connected between components that may be misaligned or movable relative to one another.

Although specific embodiments of the invention are described hereinbefore, it will be appreciated that a wide range of modifications and alterations may be made to the described embodiments without departing from the scope of the invention as defined by the appended claims.